Piezoelectric element, process for producing the same and ink jet recording head

ABSTRACT

Provided are a piezoelectric element by which a pressure of a better displacement is obtained, a process for producing the same and an ink jet recording head having the piezoelectric element.  
     A piezoelectric element comprising a substrate ( 2 ), a lower electrode ( 3 ) formedon the substrate ( 2 ), piezoelectric film ( 7 )[( 4 )( 5 )( 6 )] each containing Pb (Zr 1−x Ti x )O 3  (0&lt;x&lt;1) and a valence compensation-type perovskite represented by formula Pb(A 1/3  B 2/3 )O 3  (wherein A and B each represent a valence compensation-type perovskite) as basic components formed on the lower electrode ( 3 ), and an upper electrode ( 8 ) formed on the piezoelectric film ( 7 ). In the piezoelectric film, the concentration of A and/or B is changed in the thickness direction of the piezoelectric film, and the maximum value of the concentration of A and/or B is shown in a region within 60% from the upper electrode side in the thickness direction of the piezoelectric film. It is suited for an ink jet recording head.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a piezoelectric element. Morespecifically, it relates to a piezoelectric element in which a componentconcentration in a thickness direction of a piezoelectric film ischanged to obtain a pressure of a better displacement. Further, itrelates to a process for producing the piezoelectric element. Stillfurther, it relates to an ink jet recording head having thepiezoelectric element.

[0003] 2. Description of the Related Art

[0004] A piezoelectric film element having a piezoelectric film and anelectrode is quite important as, for example, an actuator of an ink jetrecording head, a micropump, a micromachine, a micromirror device or anultrasonic vibrator. An ink jet recording head using a piezoelectricelement has generally an ink chamber communicated with a nozzle and anink supply unit, and it jets ink droplets from the nozzle by changing avolume of the ink chamber with a piezoelectric element. A piezoelectricelement used in an ink jet recording head includes various types. Forexample, Japanese Examined Patent Publication No.53-12,138/1978 andJapanese Laid-Open Patent Publication No.6-40,030/1994 disclose a headusing a piezoelectric element of a bending mode such as bimorph orunimorph. In the bending mode, a volume of an ink chamber is changed bybending a piezoelectric element constituting a part of a wall of an inkchamber like bimetal. In a part (substrate of a piezoelectric element)of a wall of an ink chamber, a lower electrode, a piezoelectric film andan upper electrode are laminated in this order. The piezoelectric filmis polarized in a film thickness direction, and actuated in a d31 mode.For example, when an electric field of a direction in which thepiezoelectric film is shrunk in a direction parallel to the surface isapplied to both electrodes, the piezoelectric element is bent from thepiezoelectric film toward the substrate in a perpendicular direction tothe substrate. When an electric field of an opposite direction isapplied, the piezoelectric film is extended, and the piezoelectricelement is bend from the substrate toward the piezoelectric film.

[0005] In the piezoelectric element employed in this usage, satisfactorymechanical characteristics (pressure of a displacement) have to beobtained.

[0006] Japanese Laid-Open Patent Publication No. 10-290,035/1998describes that a piezoelectric strain constant is stabilized by applyingconcentration gradients of zirconium and titanium in a film thicknessdirection and controlling heat generation of a piezoelectric film.

[0007] Japanese Laid-Open Patent Publication No.9-92,897/1997 describesa piezoelectric film in which a concentration of at least one of A and Bof formula Pb(A×By)O₃ (x+y=1) is changed in a film thickness directionof the piezoelectric film and a concentration of at least one of A and Bshows a maximum value in an interface between the piezoelectric film anda lower electrode.

[0008] Japanese Laid-Open Patent Publication No. 10-139,594/1998describes that in order not to decrease a piezoelectric strain constant,a piezoelectric film is composed of a large number of layers, a mainlayer being made of a three-component material comprising lead magnesiumniobate, lead zirconate (PZ) and lead titanate (PT) and a partial layerbeing made of a two-component material comprising lead zirconatetitanate (PZT).

SUMMARY OF THE INVENTION

[0009] The object of the present invention is to provide a piezoelectricelement that provides a pressure of an excellent displacement ascompared with an ordinary piezoelectric element. Further, the object ofthe present invention is to provide a process for producing thepiezoelectric element. Still further, the object of the presentinvention is to provide an ink jet recording head having thepiezoelectric element.

[0010] The present inventors have assiduously conducted investigations,and have consequently found that the aim of the present invention isattained by a piezoelectric film in which a maximum value of aconcentration of A and/or B of a basic component Pb (A_(1/3) B_(2/3))O₃of a piezoelectric film is present in a region within 60% from an upperelectrode side in a thickness direction of the piezoelectric film. Thisfinding has led to the completion of the present invention.

[0011] That is, the present invention relates to a piezoelectric elementcomprising a substrate, a lower electrode formed on the substrate, apiezoelectric film containing Pb (Zr_(1-x)Ti_(x))O₃ (0<x<1) and avalence compensation-type perovskite represented by general formulaPb(A_(1/3)B_(2/3))O₃ (wherein A and B each represent a metal elementcapable of forming the valence compensation-type perovskite) as basiccomponents formed on the lower electrode, and an upper electrode formedon the piezoelectric film,

[0012] wherein in any arbitrary regions in the thickness direction ofthe piezoelectric film, Pb (Zr_(1-x)Ti_(x))O₃ and the valencecompensation-type perovskite represented by the general formulaPb(A_(1/3) B_(2/3))O₃ are contained,

[0013] in any arbitrary regions in the thickness direction of thepiezoelectric film, a concentration of the valence compensation-typeperovskite represented by the general formula Pb(A_(1/3) B_(2/3))O₃ iswithin a range of 20 to 40 mole %, and

[0014] in the piezoelectric film, a concentration of A and/or B ischanged in the thickness direction of the piezoelectric film and themaximum value of the concentration of A and/or B is shown in a regionwithin 60% from the upper electrode side in the thickness direction ofthe piezoelectric film.

[0015] Preferable is a piezoelectric element in which in thepiezoelectric film, the concentration of A and/or B is changed in thethickness direction of the piezoelectric film and the maximum value ofthe concentration of A and/or B is shown in a region within 40% from theupper electrode side in the thickness direction of the piezoelectricfilm.

[0016] By changing the concentration of A and/or B in the film thicknessdirection and providing the maximum value, the greater displacement ofthe piezoelectric film is obtained.

[0017] To obtain higher effects, Pb (Zr_(1-x) Ti_(x))O₃ and the valencecompensation-type perovskite represented by the general formulaPb(A_(1/3) B_(2/3))O₃ are contained in any arbitrary regions in thethickness direction of the piezoelectric film, and a concentration ofthe valence compensation-type perovskite represented by the generalformula Pb(A_(1/3) B_(2/3))O₃ is within a range of 20 to 40 mole % inany arbitrary regions in the thickness direction of the piezoelectricfilm.

[0018] It is preferable that in the piezoelectric film, theconcentration of A and/or B is changed in the thickness direction of thepiezoelectric film and the minimum value of the concentration of Aand/or B is shown in a region within 20% from the lower electrode sidein the thickness direction of the piezoelectric film.

[0019] In the present invention, the thickness of the piezoelectric filmis preferably between 1 and 25 μm in view of the use as an actuator ofan ink jet recording head. It is more preferably between 1 and 12 μm.The piezoelectric film is composed of, preferably, 2 to 10 layersdifferent in composition, more preferably 3 to 8 layers different incomposition.

[0020] In the present invention, it is preferable that A represents anelement selected from the group consisting of alkaline earthmetals, Mn,Fe, Co, Ni, Cu and Zn andB represents an element selected from the groupconsisting of V, Nb and Ta. Examples of the alkaline earth metalsinclude Mg, Ca, Sr and Ba.

[0021] Further, it is preferable that A represents an element selectedfrom the group consisting of Mg, Ni and Zn and B represents an elementselected from the group consisting of Nb and Ta.

[0022] It is preferable that the piezoelectric film of the piezoelectricelement of the present invention further contains (Ba_(1−y) Sr_(y))TiO₃(0≦y≦1) as a third component.

[0023] The piezoelectric film of the piezoelectric element of thepresent invention is preferably formed by a gaseous phase method in thepoint of view of durability of the elements. Examples of the gaseousphase method include a sputtering method, a vacuum deposition method, aCVD (Chemical Vapor Deposition) method and a laser ablation method. A RFmagnetron sputtering method and a MOCVD (Metal Organic Chemical VaporDeposition) method are more preferable. By forming the piezoelectricfilm by the gaseous method, the film having a more excellent mechanicalstrength is obtained and a durability of the piezoelectric element isimproved.

[0024] The present invention also relates to a process for producing thepiezoelectric element. A process for producing the piezoelectric elementin the present invention comprises a step of forming a piezoelectricfilm on a lower electrode and a step of forming an upper electrode onthe piezoelectric film,

[0025] the step of forming the piezoelectric film being conducted usinga composition containing piezoelectric materials capable of forming thetwo basic components and, as required, the third component and/orprecursors thereof.

[0026] Moreover, the present invention relates to an ink jet recordinghead having the piezoelectric element or the piezoelectric elementproduced by the process. The ink jet recording head comprises at least anozzle, an ink chamber, an ink supply unit and a piezoelectric element,the nozzle and the ink supply unit being communicated with the inkchamber. More specifically it relates to an ink jet recording head usinga piezoelectric element of a bending mode in which a substrate of thepiezoelectric element serves also as a part of a wall of the inkchamber.

[0027] The ink jet recording head includes, for example, a head of amulti-nozzle in which plural nozzles are arranged in straight line or inzigzag fashion.

[0028] The ink jet recording head of the present invention can provide asatisfactory amount of displacement by using the piezoelectric elementand can jet ink by variously changing a volume of one droplet uponcontrolling the amount of displacement. That is, an ink jet recordinghead is obtained which can control a volume of one droplet to be jettedover a wide range as compared with an ordinary head.

[0029] According to the present invention, a piezoelectric element isprovided which gives a pressure of an excellent displacement. Thispiezoelectric element is preferably used in an ink jet recording head inparticular, and this head can control the volume of one droplet to bejetted over a wide range as compared with an ordinary head.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 is a sectional view showing an example of a simplifiedstructure of a piezoelectric element of the present invention.

[0031]FIG. 2 is a sectional view showing an example of a simplifiedstructure of an ink jet recording head using the piezoelectric elementof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0032] In the present invention, the piezoelectric film containsPb(Zr_(1−x) Ti_(x))O₃ (0<x<1) and a valence compensation-type perovskiterepresented by formula Pb(A_(1/3) B_(2/3))O₃ (wherein A and B eachrepresent a metallic element capable of forming a valencecompensation-type perovskite) as basic components.

[0033] It is preferable that A represents an element selected from thegroup consisting of alkaline earth metals such as Mg, Ca, Sr and Ba, Mn,Fe, Co, Ni, Cu and Zn, and B represents an element selected from V, Nband Ta. Further, it is preferable that A represents an element selectedfrom Mg, Ni and Zn and B represents an element selected from Nb and Tabecause a greater amount of displacement is obtained in case of the useas a piezoelectric element.

[0034] It is preferable that the piezoelectric film of the piezoelectricelement of the present invention further contains (Ba_(1−y) Sr_(y))TiO₃(0≦y≦1, hereinafter referred to as “BST”) as a third component. Forexample, BaTiO₃ or SrTiO₃ is preferably used. By incorporating BST inthe piezoelectric film, a leakage resistance and piezoelectriccharacteristics of the piezoelectric element can be improved.

[0035] In the present invention, the concentration of A and/or B ischanged in the thickness direction of the piezoelectric film, and themaximum value of the concentration of A and/or B is present in a regionwithin 60% from the upper electrode side in the thickness direction ofthe piezoelectric film. This construction provides a greaterdisplacement of the piezoelectric film. It is preferable that themaximum value of the concentration of A and/or B is present in a regionwithin 40% from the upper electrode side in the thickness direction ofthe piezoelectric film.

[0036] Further, it is preferable that the minimum value of theconcentration of A and/or B is present in a region within 20% from thelower electrode side in the thickness direction of the piezoelectricfilm. When the maximum value is present in this region and the minimumvalue is present in this region, a still greater displacement of thepiezoelectric film is obtained.

[0037] When the piezoelectric element is used as an actuator of an inkjet recording head, the thickness of the piezoelectric film ispreferably between 1 and 25 μm, more preferably between 1 and 12 μm.When it is used as the actuator of the ink jet recording head, this filmthickness is appropriate.

[0038] In the present invention, the concentration of A and/or B in thefilm thickness direction may be changed either continuously ordiscontinuously.

[0039] The piezoelectric film showing the continuous change of theconcentration is formed upon continuously changing compositions ofstarting materials by a sputtering method, a vacuum deposition method, aCVD (Chemical Vapor Deposition) method or a laser ablation method. Thepiezoelectric film showing the discontinuous change of the concentrationis prepared by forming plural layers different in composition by theforegoing method or a coating method. In either case, it is requiredthat the maximum value of the concentration of A and/or B is present ina region within 60% from the upper electrode in the thickness directionof the piezoelectric film.

[0040] When the concentration of A and/or B is changed discontinuously,the piezoelectric film is composed of at least 2 layers different incomposition. The piezoelectric film is composed of, preferably, 2 to 10layers different in composition, more preferably, 3 to 8 layersdifferent in composition. In view of the production, a structure made of2 or 3 layers is preferable. A structure made of more than 10 layers isnot problematic at all in view of the performance of the piezoelectricfilm. However, a structure made of 10 layers or less is preferable inview of the production cost. Further, with respect to plural layersdifferent in composition, it is not required in particular that all ofthe layers are different in composition. For example, in case thepiezoelectric film is made of 5 layers different in composition, thecompositions of the 1st layer and the 3rd layer counted from the upperelectrode side may be the same. Any structure will do so long as themaximum value of the concentration of A and/or B is present in theregion within 60% from the upper electrode side in the thicknessdirection of the piezoelectric film.

[0041] The film thickness of each layer constituting the piezoelectricfilm is not particularly limited, and any film thickness will do so longas a satisfactory effect of displacement is obtained in the formation ofthe piezoelectric film. The film thickness of each layer canappropriately be determined, as required, in consideration of the changein composition of layers used, the layer structure and the filmthickness of the overall piezoelectric film. For example, the filmthickness of each layer is appropriately between 0.1 and 12.5 μm,preferably between 0.5 and 4 μm. Further, the film thicknesses of therespective layers are not necessarily the same.

[0042] Any material can be used in the substrate so long as itwithstands calcination conditions of the piezoelectric film, and it isnot particularly limited. Examples thereof include ceramics, glass and ametal. Specific examples thereof include zirconia, alumina, magnesia,silicon nitride, aluminum nitride, silicon carbide, silicon oxide andsilicon. The thickness of the substrate is not particularly limited. Itis preferably between 1 μm and 100 μm, more preferably between 1 μm and50 μm.

[0043] The material of the lower electrode is not particularly limited,and any material which is ordinarily used in a piezoelectric element isavailable. Examples thereof include Pt and Au. A method for forming thelower electrode is not particularly limited. It is formed by, forexample, a thick film method, a sputtering method or a depositionmethod. The thickness of the lower electrode is not particularlylimited. It is preferably between 0.05 μm and 15 μm.

[0044] The surface of the substrate on which the lower electrode isformed may be subjected to an appropriate surface treatment in advance.For example, the surface may be formed of a silane coupling agent.

[0045] The electrode material is not particularly limited either. Anymaterial which is ordinarily used in a piezoelectric element isavailable. Examples thereof include Pt and Au. A method for forming theupper electrode is not particularly limited. It is formed by, forexample, a thick film method, a sputtering method or a depositionmethod. The thickness of the upper electrode is not particularly limitedeither. It is, for example, between 0.05 μm and 15 μm.

[0046] Further, a contact layer may be interposed between the lowerelectrode and the piezoelectric film or between the piezoelectric filmand the upper electrode. As the contact layer, a layer containingtitanium, chromium or titanium oxide is proposed.

[0047] A process for producing the piezoelectric element in the presentinvention is described below.

[0048] The process in the present invention comprises a step of forminga lower electrode on a substrate, a step of forming a piezoelectric filmon the lower electrode and a step of forming an upper electrode on thepiezoelectric film.

[0049] The piezoelectric film is formed by, for example, a sputteringmethod, a vacuum deposition method, a CVD method, a laser ablationmethod or a coating method using a composition containing piezoelectricmaterials capable of forming the two basic components and, as required,the third component and/or precursors thereof.

[0050] The piezoelectric film in which the concentration of A and/or Bis continuously changed is produced by, for example, a sputteringmethod, a vacuum deposition method, a CVD method or a laser ablationmethod upon continuously changing compositions of starting materials asdescribed above.

[0051] The formation of the plural layers different in composition whichconstitute the piezoelectric film can be conducted by the foregoingmethod or a coating method. The coating method is preferable because theproduction step is simple.

[0052] In the coating method, the composition containing thepiezoelectric materials and/or precursors thereof may be a paste or acoating solution. The paste or the coating solution is coated to formeach layer successively.

[0053] The paste of the composition is obtained by kneading a perovskitepowder for forming each layer, a solvent and an organic polymer as abinder.

[0054] The perovskite powder is not particularly limited. However, forobtaining uniform film properties, a particle diameter measured by theBET method is preferably 0.5 μm or less, more preferably 0.2 μm or less.

[0055] The concentration of the oxide in the composition paste ispreferably between 70 and 98% by weight, more preferably between 80 and95% by weight.

[0056] The solvent is not particularly limited, and it is selected fromvarious known solvents as required. Appropriate examples of the solventinclude hydrophilic solvents, for example, alcohols such as methanol,ethanol, propanol and 2-ethoxyethanol, and ethers such as carbitol,butoxyethoxycarbitol and ethyl cellosolve.

[0057] An appropriate organic polymer is not particularly limited.Examples thereof include celluloses such as hydroxyethylcellulose andhydroxypropylcellulose (HPC), vinyl polymers such as polyvinyl alcohol(PVA), polyvinyl butyral (PVB), polyacrylic ester and polymethacrylicester, polyethylene glycol (PEG), polyethylene oxide (PEO), an epoxyresin, a phenol resin, polyethylene terephthalate (PET) and a nylonresin. The amount of the organic polymer is not particularly limited. Itcan be selected from, for example, the range of 1 to 40% by weight,preferably the range of 5 to 20% by weight based on inorganic oxides.

[0058] The paste can also contain various known additives such as adispersing agent, a plasticizer, a defoamer and a photo-curing agent asrequired.

[0059] The coating method is not particularly limited. It can includeordinary methods such as a spin coating method, a dipping method, acasting method, a screen printing method and a doctor blade method.After the coating, the solvent is removed by drying as required.

[0060] The coating solution of the composition is obtained bypolymerizing a starting metal-containing compound (for example, a metalalkoxide) by a sol-gel method to form a precursor sol of a ferroelectricoxide. That is, the “precursor” of the ferroelectric oxide refers to aprecursor which is obtained by the sol-gel method and converted into asubstantially complete metal oxide.

[0061] The sol-gel method is a known method. For example, a precursorsol of lead zirconate titanate (PZT) can be obtained by hydrolyzing andpolymerizing a titanium alkoxide, a zirconium alkoxide and a leadalkoxide or lead acetate. A desired metal-containing compound can beused as a starting material.

[0062] A solvent for hydrolysis/polymerization reaction is notparticularly limited so long as it can dissolve a starting material suchas an alkoxide or the like and water and is not coagulated at atemperature at which to add water. For example, as a polar solvent,alcohols such as methanol, ethanol and propanol can preferably be used.Further, a non-polar solvent such as toluene may be mixed at anappropriate ratio.

[0063] The hydrolysis/polymerization reaction can usually be conductedin the presence of an appropriate acid catalyst at −100 to 200° C.,though it depends on a starting material such as an alkoxide or thelike. In this manner, the coating solution of the composition containingthe piezoelectric materials and/or precursors thereof can be obtained.

[0064] An appropriate organic polymer can be added to the coatingsolution of the piezoelectric composition. The organic polymer is notparticularly limited. Examples thereof include celluloses such ashydroxyethylcellulose and hydroxypropylcellulose (HPC), vinyl polymerssuch as polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyacrylicester and polymethacrylic ester, polyethylene glycol (PEG), polyethyleneoxide (PEO), an epoxy resin, a phenol resin, polyethylene terephthalate(PET) and a nylon resin. Any polymer which can uniformly be incorporatedin the coating solution is available.

[0065] Further, the amount of the organic polymer is not particularlylimited. It can be selected from, for example, the range of 1 to 40% byweight, preferably the range of 5 to 20% by weight based on inorganicoxides. When the amount of the organic polymer exceeds 40% by weight, anappropriate film is hardly obtained even by heat treatment.

[0066] The coating solution can further contain various known additivessuch as a dispersing agent, a plasticizer, a defoamer and a photo-curingagent as required.

[0067] The coating method is not particularly limited. It can includeordinary coating methods such as a spin coating method, a dippingmethod, a casting method, a spray coating method, a die coating method,a screen printing method and a doctor blade method. After the coating,the solvent is removed by drying as required.

[0068] After the paste or the coating solution is coated, calcination isconducted. The calcination can be conducted at an appropriatetemperature of, for example, 300 to 1,400° C., preferably 600 to 1,200°C., though it varies depending on the type of the paste or the coatingsolution and the amounts of the components. Further, it can be conductedin any atmosphere such as an inert gas atmosphere, a lead oxideatmosphere or an oxygen-containing atmosphere (for example, air) undernormal pressure or reduced pressure. The calcination is preferablyconducted in air at a temperature of room temperature to 300 though1,400° C. for several seconds to 24 hours. Further, the temperature maygradually be raised. In this calcination, the organic component isremoved almost completely, and a dense piezoelectric film is obtained.

[0069] The lower electrode can be formed on the substrate by a usualmethod. It is advisable that the formation is conducted by, for example,a thick film method such as screen printing, a sputtering method or adeposition method. The upper electrode can.also be formed on thepiezoelectric film by a usual method. It is advisable that the formationis conducted by, for example, a thick film method, a sputtering methodor a deposition method.

[0070] The elemental analysis of the piezoelectric film can be conductedby X-ray microanalysis (EPMA) in case of a film thickness ofapproximately 10 μm and by X-ray photoelectron spectroscopic analysis(ESCA), secondary ion mass spectroscopy (SIMS) or Auger electronanalysis (AES) in case of a film thickness of approximately severalmicrometers.

[0071] The present invention also relates to an ink jet recording headhaving the piezoelectric element or the piezoelectric element obtainedby the process as an actuator. The ink jet recording head includes ahead of a multi-nozzle in which plural nozzles are arranged in straightline or in zigzag fashion too.

EXAMPLES

[0072] The present invention is illustrated more specifically byreferring to the following Examples. However, the present invention isnot limited thereto.

Examples 1 to 11 and Comparative Examples 1 to 3

[0073] (Formation of Piezoelectric Pastes)

[0074] Each (85 parts by weight) of perovskite powders havingcompositions shown below was kneaded with 6.5 parts by weight of ethylcellosolve, 0.5 part by weight of polyethyl acrylate and 8 parts byweight of hydroxypropylcellulose to form a piezoelectric paste having anoxide concentration of 85% by weight.

[0075] The compositions of the following pastes are typical examples,and pastes having various other compositions are also available.

[0076] Paste 1

[0077] 0.2OPb(Mg_(1/3) Nb_(2/3))O₃−0.80Pb(Zr_(0.4) Ti_(0.6))O₃

[0078] Paste 2

[0079] 0.35Pb(Mg_(1/3) Nb_(2/3))O₃−0.65Pb(Zr_(0.4) Ti_(0.6))O₃

[0080] Paste 3

[0081] 0.3OPb(Mg_(1/3) Nb_(2/3))O₃−0.67Pb(Zr_(0.4)Ti_(0.6))O₃−0.03SrTiO₃

[0082] Paste 4

[0083] 0.4OPb(Mg_(1/3) Nb_(2/3))O₃−0.55Pb(Zr_(0.4) Ti_(0.6))O₃−0.05SrTi_(0.3)

[0084] Paste 5

[0085] 0.2OPb(Zn_(1/3) Nb_(2/3))O₃−0.80Pb(Zr_(0.4) Ti_(0.6))O₃

[0086] Paste 6

[0087] 0.3OPb(Zn_(1/3) Nb_(2/3))O₃−0.70Pb(Zr_(0.4) Ti_(0.6))O₃

[0088] Paste 7

[0089] 0.40Pb(Zn_(1/3) Nb_(2/3))O₃−0.60Pb(Zr_(0.4) Ti_(0.6))O₃

[0090] Paste 8

[0091] 0.20Pb(Mg_(1/3) Ta_(2/3))O₃−0.80Pb(Zr_(0.4) Ti_(0.6))O₃

[0092] Paste 9

[0093] 0.25Pb(Mg_(1/3) Ta_(2/3))O₃−0.75Pb(Zr_(0.4) Ti_(0.6))O₃

[0094] Paste 10

[0095] 0.30Pb(Mg_(1/3) Ta_(2/3))O₃−0.70Pb(Zr₀ ₄ Ti_(0.6))O₃

[0096] Paste 11

[0097] 0.35Pb(Mg_(1/3) Ta_(2/3))O₃−0.65Pb(Zr_(0.4) Ti_(0.6))O₃

[0098] Paste 12

[0099] 0.40Pb(Mg_(1/3) Ta_(2/3))O₃−0.60Pb(Zr_(0.4) Ti_(0.6))O₃

[0100] Paste 13

[0101] 0.25Pb(Mg_(1/3) Ta_(2/3))O₃−0.73Pb(Zr_(0.4)Ti_(0.6))O₃−0.02(Ba_(0.5) Sr_(0.5))Ti_(0.3)

[0102] Paste 14

[0103] 0.30Pb(Mg_(1/3) Ta_(2/3))O₃−0.66Pb(Zr_(0.4)Ti,.₆)O₃−0.04(Ba_(0.6) Sr_(0.4))Ti_(0.3)

[0104] Paste 15

[0105] 0.35Pb(Mg_(1/3) Ta_(2/3))O₃−0.59Pb(Zr_(0.4)Ti_(0.6))O₃−0.06(Ba_(0.7) Sr_(0.3))Ti_(0.3)

[0106] Paste 16

[0107] 0.20Pb(Ni_(1/3) Nb_(2/3))O₃−0.75Pb(Zr_(0.4)Ti_(0.6))O₃−0.05BaTi_(0.3)

[0108] Paste 17

[0109] 0.35Pb(Ni_(1/3) Nb_(2/3))O₃−0.60Pb(ZrO₄ Ti₀₆)O₃−0.05BaTi_(0.3)

[0110] Paste 18

[0111] 0.20Pb(Mn_(1/3) V_(2/3))O₃−0.80Pb(Zr_(0.4) Ti_(0.6))O₃

[0112] Paste 19

[0113] 0.30Pb(Mn_(1/3) V_(2/3))O₃−0.70Pb(Zr_(0.4) Ti_(0.6))O₃

[0114] Paste 20

[0115] 0.35Pb(Mn_(1/3) V_(2/3))O₃−0.65Pb(Zr_(0.4) Ti_(0.6))O₃

[0116] Paste 21

[0117] 0.20Pb(Co_(1/3) V_(2/3))O₃−0.80Pb(Zr_(0.4) Ti_(0.6))O₃

[0118] Paste 22

[0119] 0.30Pb(Co_(1/3) V_(2/3))O₃−0.70Pb(Zr_(0.4) Ti_(0.6))O₃

[0120] Paste 23

[0121] 0.35Pb(Co_(1/3) V_(2/3))O₃−0.65Pb(Zr O₄ Ti_(0.6))O₃

[0122] Paste 24

[0123] 0.40Pb(Co_(1/3) V_(2/3))O₃−0.60Pb(Zr_(0.4) Ti_(0.6))O₃

[0124] Paste 25

[0125] 0.20Pb(Cu_(1/3) V_(2/3))O₃−0.80Pb(Zr_(0.4) Ti_(0.6))O₃

[0126] Paste 26

[0127] 0.25Pb(Cu_(1/3) V_(2/3))O₃−0.75Pb(Zr_(0.4) Ti_(0.6))O₃

[0128] Paste 27

[0129] 0.30Pb(Cu_(1/3) V_(2/3))O₃−0.70Pb(ZrO,₄ Ti_(0.6))O₃

[0130] Paste 28

[0131] 0.35Pb(Cu_(1/3) V_(2/3))O₃−0.65Pb(Zr_(0.4) Ti_(0.6))O₃

[0132] Paste 29

[0133] 0.40Pb(Cu_(1/3) V_(2/3))O₃−0.60Pb(Zr_(0.4) Ti_(0.6))O₃

[0134] Paste 30

[0135] Pb(Zr_(0.4) Ti_(0.6))O₃

[0136] Paste 31

[0137] 0.06Pb(Zn_(1/3) Nb_(2/3))O₃−0.94Pb(Zr_(0.4) Ti_(0.6))O₃

[0138] Paste 32

[0139] 0.12Pb(Zn_(1/3) Nb_(2/3))O₃−0.88Pb(Zr_(0.4) Ti_(0.6))O₃

[0140] Paste 33

[0141] 0.18Pb(Zn_(1/3) Nb_(2/3))O₃−0.82Pb(Zr_(0.4) Ti_(0.6))O₃

[0142] Paste 34

[0143] 0.42Pb(Zn_(1/3) Nb_(2/3))O₃−0.58Pb(Zr_(0.4) Ti_(0.6))O₃

[0144] Paste 35

[0145] 0.48Pb(Zn_(1/3) Nb_(2/3))O₃−0.52Pb(Zr_(0/4) Ti_(0.6))O₃

[0146] Paste 36

[0147] 0.54Pb(Zn_(1/3) Nb_(2/3))O₃−0.46Pb(Zr_(0.4) Ti_(0.6))O₃

[0148] (Preparation of Piezoelectric Elements)

[0149] In Examples 1 to 11, piezoelectric elements for an ink jetrecording head each having a piezoelectric film composed of plurallayers different in composition were prepared using plural pastes amongthe pastes different in composition as listed above. Table 1 shows thenumber of layers different in composition which constitute thepiezoelectric film, the type of the paste used in each layer and thethickness of each layer after calcination. The respective layersconstituting the piezoelectric film were numbered in order from thelower electrode side.

[0150]FIG. 1 shows a piezoelectric element (1) having a three-layerstructure which is an example of a piezoelectric element for an ink jetrecording head having a piezoelectric film composed of plural layersdifferent in composition. That is, a Pt paste was screen-printed on azirconia substrate (2) having a thickness of 10 μm as a diaphragm suchthat the thickness after calcination became 5 μm to form a lowerelectrode (3).

[0151] Pastes for forming layers shown in Table 1 were laminated on thelower electrode (3) in order from a 1st layer (4) to an uppermost layer[3rd layer (6) in an example of FIG. 1] through screen printing to forma multilayer film (7). At this time, the film thickness of each layerwas adjusted such that the thickness after calcination reached a valueshown in Table 1, and a size of a piezoelectric material was adjusted to200 μm×3 mm. After the resulting multilayer film (7) was calcined at1,200° C. for 2 hours, an Au film was formed on the piezoelectric filmby a sputtering method as an upper electrode (8) to obtain apiezoelectric element (1).

[0152] The selection of the paste and the selection of the thickness ofeach layer in Examples can be changed as required, and those in Examplesare only illustrative.

[0153] In Comparative Examples 1 and 2, piezoelectric elements eachhaving a single-layer piezoelectric film were prepared as in Examples 1to 11 except using conditions shown in Table 1.

[0154] In Comparative Examples 3, 7 and 8, a piezoelectric elementhaving a piezoelectric film composed of plural layers different incomposition was prepared as in Examples 1 to 11 except using conditionsshown in Table 1.

[0155] (Analysis and Evaluation of Piezoelectric Elements)

[0156] In each of the piezoelectric elements obtained in Examples 1 to11 and Comparative Examples 3, 7 and 8, the change in concentration ofthe valence compensation-type perovskite metal element contained in eachpiezoelectric film in the thickness direction of the piezoelectric filmwas analyzed using EPMA. At this time, the position of the maximumconcentration was shown by percentage from the upper electrode side, andthe position of the minimum concentration by percentage from the lowerelectrode side. The results of analysis are shown in Table 1. Analysiswas conducted on vanadium in Examples 1, 2, 3, 10 and 11 and ComparativeExample 3, on niobium in Examples 4, 5 and 7 and Comparative Examples 7and 8 and on magnesium in Examples 6, 8 and 9.

[0157] The piezoelectric elements obtained in Examples 1 to 11 andComparative Examples 1 to 3 were evaluated as follows. A vibration widthof the elements in application of a voltage was measured using a Tencormeter. Since the film compositions of the elements were different andapplied voltages for obtaining the maximum vibration width weredifferent, the vibration width was evaluated by a value with which toprovide the maximum vibration without unifying the applied voltage. Theresults of evaluation are shown in Table 1. As shown in Table 1, theelements obtained in Examples 1 to 11 provided the great vibration widthcompared with those in Comparative Examples 1 to 3 and ComparativeExamples 7 and 8.

[0158] These results are due to the reasons that, in Examples 1 to 11,Pb (Zr_(1−x) Ti_(x))O₃ (0<x<1) and the valence Ho compensation-typeperovskite represented by the general formula Pb(A_(1/3) B_(2/3))O₃ arecontained in each layer which composes the piezoelectric film, and theconcentration of the valence compensation-type perovskite represented bythe general formula Pb(A_(1/3) B_(2/3))O₃ is within a range of 20 to 40mole % in each layer which composes the piezoelectric film.

[0159] Further, in Examples 1 to 11, the great vibration width wasobtained especially in Examples 7 to 9. These results are due to thereason that (Ba_(1−y) Sr_(y))Ti_(0.3) (0≦y≦1) is contained in thepiezoelectric film in Examples 7 to 9.

[0160] Each leak current of the elements of Examples 4 and 7 inapplication of 50 V was measured. The leak current of Example 7 showedtwo figures smaller than that of Example 4. These results are also dueto the reason that (Ba_(1−y) Sr_(y))TiO₃ (0≦y≦1) is contained in thepiezoelectric film in Example 7. TABLE 1 Position of Position of Type ofpaste Thickness of layer (μm) Vibration maximum minimum Number 1st 2nd3rd 4th 5th 1st 2nd 3rd 4th 5th width concentration concentration oflayers layer layer layer layer layer layer layer layer layer layer (μm)(%) (%) Ex. 1 2 18 20 — — — 6 4 — — — 0.33 0-32 0-55 Ex. 2 3 21 22 24 —— 2 4 4 — — 0.34 0-36 0-17 Ex. 3 5 25 26 27 28 29 2 2 2 2 2 0.35 0-180-16 Ex. 4 2  1  2 — — — 6 4 — — — 0.40 0-35 0-54 Ex. 5 3  5  6  7 — — 24 4 — — 0.42 0-36 0-18 Ex. 6 5  8  9 10 11 12 2 2 2 2 2 0.42 0-17 0-18Ex. 7 2 16 17 — — — 6 4 — — — 0.43 0-34 0-56 Ex. 8 3  1  3  4 — — 2 4 4— — 0.44 0-35 0-16 Ex. 9 5  8 13 14 15 12 2 2 2 2 2 0.44 0-18 0-17 Ex.10 3 18 20 30 — — 5 3 2 — — 0.31 37 93-100 Ex. 11 3 21 23 22 — — 3 3 4 —— 0.27 54 0-16 CEx. 1 1 30 — — — — 10  — — — — 0.21 — — CEx. 2 1 27 — —— — 10  — — — — 0.21 — — CEx. 3 5 29 28 27 26 25 2 2 2 2 2 0.18 93-10094-100 CEx. 7 3 31 32 33 — — 2 4 4 — — 0.24 0-34 0-15 CEx. 8 3 34 35 36— — 2 4 4 — — 0.23 0-33 0-14

[0161] An ink jet recording head was produced using each of thepiezoelectric elements obtained in Examples 1 to 11. FIG. 2 is asectional view showing a simplified structure thereof. A flow path plate(9) was formed with silicon, and a nozzle plate (10) with a stainlesssteel. A nozzle (11) communicated with an ink chamber (13) was formed inthe nozzle plate (10). Ink was supplied from an ink tank (not shown inFIG. 2) to the ink chamber (13) via an ink supply path (12), and jettedfrom the nozzle (11).

[0162] Ink was jetted using each of the ink jet recording heads byapplying a driving signal repeated at a frequency of 10 kHz to thepiezoelectric element. Then, a satisfactory jet power was obtained.Further, when a waveform of the driving signal was changed in the inkjet recording head obtained from the piezoelectric element in Example 6as required, the volume of an ink droplet could be controlled in therange of 2 pl to 31 pl.

Examples 13 to 23 and Comparative Examples 4 to 6

[0163] (Formation of Piezoelectric Coating Solutions)

[0164] Dehydrated lead acetate, metallic magnesium, dehydrated zincacetate, dehydrated nickel acetate, pentaethoxyniobium,pentaethoxytantalum, tetra-i-propoxytitanium, tetra-n -butoxyzirconium,metallic barium or diethoxybarium, metallic strontium ordiethoxystrontium, dehydrated manganese acetate, triethoxyoxovanadium,dehydrated cobalt acetate and dehydrated copper acetate were used asstarting materials.

[0165] For forming each of coating solutions 1 to 30 having compositionscorresponding to the pastes 1 to 30, each of the corresponding startingmaterials was added to 2-methoxyethanol such that the molar ratio of themetal component in each coating solution was the same as that in each ofthe pastes 1 to 30. The mixture was heat-treated at 120° C. for 6 hoursto obtain a brown uniform solution. To the resulting solution was addeddropwise 0.1 M hydrochloric acid diluted with 2-ethoxyethanol. Theamount of water was the same molar amount as that of an alkoxide used. A2-methoxyethanol solution of hydroxypropylcellulose (HPC-L) was added asa thickener. The amount of hydroxypropylcellulose based on the inorganiccomposition was 10% by weight as a solid content. The oxideconcentration of the resulting coating solution was adjusted to 20% byweight. In this manner, the coating solutions 1 to 30 having the samecompositions as the pastes 1 to 30 were obtained.

[0166] (Preparation of Piezoelectric Elements)

[0167] In Examples 13 to 23, piezoelectric elements for an ink jetrecording head each having a piezoelectric film composed of plurallayers different in composition were prepared using plural coatingsolutions among the foregoing coating solutions. Table 2 shows thenumber of layers different in composition which constitute thepiezoelectric film, the type of the coating solution used in each layer,the thickness of each layer after calcination, the results of evaluationand the results of analysis. The layers constituting the piezoelectricfilm were numbered in order from the lower electrode side.

[0168]FIG. 1 shows a piezoelectric element (1) having a three-layerstructure which is an example of a piezoelectric element for an ink jetrecording head having a piezoelectric film composed of plural layersdifferent in composition. That is, a Ti film having a thickness of 50 nmand a Pt film having a thickness of 1 μm were formed in this order as alower electrode (3) on an alumina substrate (2) having a thickness of 5μm as a diaphragm by a sputtering method.

[0169] Coating solutions for forming layers shown in Table 2 werelaminated on the lower electrode (3) in order from a 1st layer (4) to anuppermost layer [3rd layer (6) in an example of FIG. 1] by a spincoating method to form a multilayer film (7). The film of each layer wasformed as follows. First, the film was formed by a spin coating method(1,200 rpm, 30 seconds) using the coating solution for forming the 1stlayer (4), then dried at 120° C., and calcined at 400° C. (rate oftemperature rise: 5° C./min, retained at 400° C. for 30 minutes). Afterthe uppermost layer was likewise laminated, the multilayer film wascalcined at 900° C. (rate of temperature rise: 10° C./min, retained at900° C. for 15 minutes). At this time, the film thickness of each layerwas adjusted such that the thickness after calcination reached a valueshown in Table 2.

[0170] A photoresist was coated on the resulting piezoelectric film, andpatterning was then conducted by exposure. A pattern of a piezoelectricmaterial was formed by chemical etching treatment such that a size ofthe piezoelectric material reached 200 μm×3 mm. An Au film was formed onthe resulting pattern of the piezoelectric material by a sputteringmethod to obtain a desired piezoelectric element (1).

[0171] In Comparative Examples 4 and 5, piezoelectric elements eachhaving a single-layer piezoelectric film were prepared as in Examples 13to 23 except using conditions shown in Table 2.

[0172] In Comparative Example 6, a piezoelectric element having apiezoelectric film composed of plural layers different in compositionwas prepared as in Examples 13 to 23 except using conditions shown inTable 2.

[0173] (Evaluation of Piezoelectric Elements)

[0174] In each of the piezoelectric elements obtained in Examples 13 to23 and Comparative Example 6, the change in concentration of the valencecompensation-type perovskite metal element contained in eachpiezoelectric film in the thickness direction of the piezoelectric filmwas analyzed using EPMA. At this time, the position of the maximumconcentration was shown by percentage from the upper electrode side, andthe position of the minimum concentration by percentage from the lowerelectrode side. The results of analysis are shown in Table 2. Analysiswas conducted on vanadium in Examples 13, 14, 15, 22 and 23 andComparative Example 6, on niobium in Examples 16, 17 and 19 and onmagnesium in Examples 18, 20 and 21.

[0175] With respect to the piezoelectric elements obtained in Examples13 to 23 and Comparative Examples 4 to 6, a vibration width wasevaluated as in Example 1. The results of evaluation are shown in Table2. As shown in Table 2, the elements obtained in Examples 13 to 23provided the great vibration width compared with those in ComparativeExamples 4 to 6.

[0176] These results are due to the reasons that, in Examples 13 to 23,Pb (Zr_(1−x) Ti_(x))O₃ (0<x<1) and the valence compensation-typeperovskite represented by the general formula Pb(A_(1/3) B_(2/3))O₃ arecontained in each layer which composes the piezoelectric film, and theconcentration of the valence compensation-type perovskite represented bythe general formula Pb(A_(1/3) B_(2/3))O₃ is within a range of 20 to 40mole % in each layer which composes the piezoelectric film.

[0177] Further, in Examples 13 to 23, the great vibration width wasobtained especially in Examples 19 to 21. These results are due to thereason that (Ba_(1−y) Sr_(y))TiO₃ (0≦y≦1) is contained in thepiezoelectric film in Examples 19 to 21.

[0178] Each leak current of the elements of Examples 16 and 19 inapplication of 50 V was measured. The leak current of Example 19 showedtwo figures smaller than that of Example 16. These results are also dueto the reason that (Ba_(1−y) Sr_(y))TiO₃ (0≦y≦1) is contained in thepiezoelectric film in Example 19. TABLE 2 Position of Position of Typeof coating solution Thickness of layer (μm) Vibration maximum minimumNumber 1st 2nd 3rd 4th 5th 1st 2nd 3rd 4th 5th width concentrationconcentration of layers layer layer layer layer layer layer layer layerlayer layer (μm) (%) (%) Ex. 13 2 18 20 — — — 6 4 — — — 0.33 0-29 0-52Ex. 14 3 21 22 24 — — 2 4 4 — — 0.35 0-30 0-15 Ex. 15 5 25 26 27 28 29 22 2 2 2 0.35 0-14 0-14 Ex. 16 2  1  2 — — — 6 4 — — — 0.41 0-30 0-53 Ex.17 3  5  6  7 — — 2 4 4 — — 0.42 0-32 0-15 Ex. 18 5  8  9 10 11 12 2 2 22 2 0.42 0-16 0-16 Ex. 19 2 16 17 — — — 6 4 — — — 0.43 0-31 0-55 Ex. 203  1  3  4 — — 2 4 4 — — 0.45 0-30 0-16 Ex. 21 5  8 13 14 15 12 2 2 2 22 0.45 0-16 0-16 Ex. 22 3 18 20 30 — — 5 3 2 — — 0.32 40 93-100 Ex. 23 321 23 22 — — 3 3 4 — — 0.27 57 0-20 CEx. 4 1 30 — — — — 10  — — — — 0.22— — CEx. 5 1 27 — — — — 10  — — — — 0.21 — — CEx. 6 5 29 28 27 26 25 2 22 2 2 0.17 94-100 94-100

[0179] An ink jet recording head was produced as in Example 1 using eachof the piezoelectric elements obtained in Examples 13 to 23. Ink wasjetted using each of the ink jet recording heads by applying a drivingsignal repeated at a frequency of 10 kHz to the piezoelectric element.Then, a satisfactory jet power was obtained. Further, when a waveform ofthe driving signal was changed in the ink jet recording head obtainedfrom the piezoelectric element in Example 18 as required, the volume ofan ink droplet could be controlled in the range of 3 pl to 29 pl.

Example 25

[0180] A piezoelectric element for an ink jet recording head having apiezoelectric film of a composition z[Pb(Mg_(1/3)Ta_(2/3))O₃]−(1−z)[Pb(Zr_(0.4) Ti_(0.6))O₃] (0≦z≦1) in which z wascontinuously changed was prepared by the MOCVD (Metal Organic ChemicalVapor Deposition) method. On a silicon substrate having a thickness of10 μm as a diaphragm, a Ti film was formed to a thickness of 50 nm and aPt film to a thickness of 0.5 μm in this order by a sputtering method toprovide a lower electrode.

[0181] A piezoelectric film of a composition z[Pb(Mg_(1/3)Ta_(2/3))0₃]−(1−z)[Pb(Zr_(0.4) Ti_(0.6))O₃] (0≦z≦1) was formed by theMOCVD method at an oxygen partial pressure of 2.2 torr and a substratetemperature of 600° C. using lead bis(dipivaloylmethanate),tetra-t-butoxyzirconium, tetra -i-propoxytitanium, magnesiumbis(dipivaloylmethanate) and pentaisopropoxytantalum as startingmaterials. In the film formation, flow rates of the starting materialswere adjusted such that z was 0.2 in the initial composition. The flowrates of the starting materials were changed such that z was graduallyincreased. When z reached 0.4, z was reduced again. The film formationwas conducted until the film thickness finally reached 8 μm. After thefilm formation, the piezoelectric film was sintered again at atemperature of 1,000° C. to provide a piezoelectric film.

[0182] A photoresist was coated on the resulting piezoelectric film, andpatterning was then conducted by exposure. A pattern of a piezoelectricmaterial was formed by chemical etching treatment such that a size ofthe piezoelectric material reached 200 μm×3 mm. An Au film was formed onthe resulting pattern of the piezoelectric material by a sputteringmethod to obtain a piezoelectric element.

[0183] EPMA analysis was conducted from the upper electrode side of thepiezoelectric film to find the positions of the maximum concentrationand the minimum concentration of magnesium in the thickness direction ofthe piezoelectric film. The position of the maximum concentration was23% from the upper electrode side, and the position of the minimumconcentration was 0 to 2% from the lower electrode side. A vibrationwidth was evaluated as in Example 1, and it was found to be 0.41 μm.

[0184] An ink jet recording head was produced as in Example 1 using thispiezoelectric element. Ink was jetted using this ink jet recording headby applying a driving signal repeated at a frequency of 10 kHz to thepiezoelectric element. When a waveform of the driving signal was changedas required, the volume of an ink droplet could be controlled in therange of 2 pl to 33 pl.

[0185] Then, using the ink jet recording head having piezoelectricelements of Examples 1 to 11, 13 to 23 and 25, a durability test of 108time continuous jets was conducted to compare the jet speed of the inkdroplet before or after the durability test in each head. The decreaseof the jet speed in the head of Example 25 showed about 5%, which wasthe smallest of all the heads. The decrease of the jet speed in theheads of Examples 1 to 23 showed within a range of 9 to 27%. Theseresults are due to the reason that the piezoelectric film of the head ofExample 25 formed by the gaseous phase method has an especiallyexcellent mechanical strength.

[0186] The present invention can be embodied in other various formswithout departing from the spirit or essential characteristics thereof.The Examples are therefore only illustrative in all respects and shallnot be interpreted in a limiting sense. Further, all changes that fallwithin meets and bounds of claims, or equivalence of such meets andbounds are within the scope of the present invention.

What is claimed is:
 1. A piezoelectric element comprising a substrate, alower electrode formed on the substrate, a piezoelectric film containingPb (Zr_(1−x) Ti_(x))O₃ (0<x<1) and a valence compensation-typeperovskite represented by general formula Pb(A_(1/3) B_(2/3))O₃ (whereinA and B each represent a metal element capable of forming a valencecompensation-type perovskite) as basic components formed on the lowerelectrode, and an upper electrode formed on the piezoelectric film,wherein in any arbitrary regions in the thickness direction of thepiezoelectric film, Pb (Zr_(1−x) Ti_(x))O₃ and the valencecompensation-type perovskite represented by the general formulaPb(A_(1/3) B_(2/3))O₃ are contained, in any arbitrary regions in thethickness direction of the piezoelectric film, a concentration of thevalence compensation-type perovskite represented by the general formulaPb(A_(1/3) B_(2/3))O₃ is within a range of 20 to 40 mole %, and in thepiezoelectric film, a concentration of A and/or B is changed in thethickness direction of the piezoelectric film and the maximum value ofthe concentration of A and/or B is shown in a region within 60% from theupper electrode side in the thickness direction of the piezoelectricfilm.
 2. The piezoelectric element according to claim 1, wherein in thepiezoelectric film, the concentration of A and/or B is changed in thethickness direction of the piezoelectric film and the maximum value ofthe concentration of A and/or B is shown in a region within 40% from theupper electrode side in the thickness direction of the piezoelectricfilm.
 3. The piezoelectric element according to claim 1, wherein in thepiezoelectric film, the concentration of A and/or B is changed in thethickness direction of the piezoelectric film and the minimum value ofthe concentration of A and/or B is shown in a region within 20% from thelower electrode side in the thickness direction of the piezoelectricfilm.
 4. The piezoelectric element according to claim 1, wherein thefilm thickness of the piezoelectric film is between 1 and 25 μm.
 5. Thepiezoelectric element according to claim 1, wherein the piezoelectricfilm is composed of plural layers different in composition.
 6. Thepiezoelectric element according to claim 5, wherein the piezoelectricfilm is composed of 2 to 10 layers different in composition.
 7. Thepiezoelectric element according to claim 1, wherein A represents anelement selected from the group consisting of alkaline earth metals, Mn,Fe, Co, Ni, Cu and Zn, and B represents an element selected from thegroup consisting of V, Nb and Ta.
 8. The piezoelectric element accordingto claim 7, wherein A represents an element selected from the groupconsisting of Mg, Ni and Zn, and B represents an element selected fromthe group consisting of Nb and Ta.
 9. The piezoelectric elementaccording to claim 1, wherein the piezoelectric film further contains(Ba_(1−y) Sr_(y))Ti_(0.3) (0≦y≦1) as a third component.
 10. Thepiezoelectric element according to claim 1, A, wherein the filmthickness of the piezoelectric film is between 1 and 12 μm.
 11. Thepiezoelectric element according to claim 5, wherein the piezoelectricfilm is composed of 3 to 8 layers different in composition.
 12. Thepiezoelectric element according to claim 1, wherein the piezoelectricfilm is formed by a gaseous phase method.
 13. The piezoelectric elementaccording to claim 12, wherein the gaseous phase method is a MOCVD(Metal Organic Chemical Vapor Deposition) method.
 14. A process forproducing the piezoelectric element according to any one of claims 1 to13, which comprises a step of forming a piezoelectric film on a lowerelectrode and a step of forming an upper electrode on the piezoelectricfilm, the step of forming the piezoelectric film being conducted using acomposition containing piezoelectric materials capable of forming thetwo basic components and, as required, the third component and/orprecursors thereof.
 15. An ink jet recording head having thepiezoelectric element according to any one of claims 1 to 13.